Comparative bioavailability of a new commercial tablet formulation and two lots of a reference formulation of haloperidol.

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The bioavailability of a new tablet formulation (5 mg) of haloperidol was estimated relative to two lots of a reference product. Twenty-eight healthy male volunteers completed all three phases in that they received the test (T) and the two reference formulations (R1 and R2) in a balanced three-way crossover design. Using a sensitive HPLC method, plasma concentrations of haloperidol and reduced haloperidol were monitored over a period of 96 h following administration of each formulation. Haloperidol was measurable in the plasma of all the volunteers, whereas reduced haloperidol was measurable in only 6 out of 28 volunteers following each administration. Therefore, the assessment of bioequivalence in this study is based on haloperidol data only. The maximum plasma concentration (Cmax), time to Cmax (tmax), and area under the curve up to the last measurable concentration (AUCot) or infinity (AUCo infinity) were compared by analyses of variance and found not to be significantly different across the formulations. The relative bioavailability based on T:R1 or T:R2 ratios of AUCo infinity, AUCot, and Cmax was, in each case, within the acceptable range of 100 +/- 20%. Also, the relative bioavailability of R1 compared with R2 was within 100 +/- 20% in terms of the above bioavailability parameters. Except for tmax, all other pharmacokinetic parameters showed wide intersubject variation.